scholarly journals The history of the muon (g-2) experiments

2019 ◽  
Author(s):  
B. Lee Roberts
Keyword(s):  
Standard Model ◽  
Quantum Electrodynamics ◽  
National Laboratory ◽  
New Physics ◽  
Brookhaven National Laboratory ◽  
Muon Decay ◽  
Higgs Bosons ◽  
The Standard Model ◽  
History Of ◽  
First Time

I discuss the history of the muon (g-2)(g−2) measurements, beginning with the Columbia-Nevis measurement that observed parity violation in muon decay, and also measured the muon gg-factor for the first time, finding g_\mu=2gμ=2. The theoretical (Standard Model) value contains contributions from quantum electrodynamics, the strong interaction through hadronic vacuum polarization and hadronic light-by-light loops, as well as the electroweak contributions from the WW, ZZ and Higgs bosons. The subsequent experiments, first at Nevis and then with increasing precision at CERN, measured the muon anomaly a_\mu = (g_\mu-2)/2aμ=(gμ−2)/2 down to a precision of 7.3 parts per million (ppm). The Brookhaven National Laboratory experiment E821 increased the precision to 0.54 ppm, and observed for the first time the electroweak contributions. Interestingly, the value of a_\muaμ measured at Brookhaven appears to be larger than the Standard Model value by greater than three standard deviations. A new experiment, Fermilab E989, aims to improve on the precision by a factor of four, to clarify whether this result is a harbinger of new physics entering through loops, or from some experimental, statistical or systematic issue.

scholarly journals SEARCHES FOR NEW PARTICLES

2002 ◽  
Vol 17 (23) ◽  
pp. 3336-3351 ◽  
Author(s):  
GAIL G. HANSON
Keyword(s):  
Standard Model ◽  
Top Quark ◽  
New Physics ◽  
Higgs Bosons ◽  
Standard Model Higgs Boson ◽  
The Past ◽  
Flavor Changing ◽  
The Standard Model ◽  
The Status ◽  
New Particles

The status of searches for new particles and new physics during the past year at the Fermilab Tevatron, at HERA and at LEP is summarized. A discussion of the hints for the Standard Model Higgs boson from LEP2 data is presented. Searches for non-Standard Model Higgs bosons are also described. Many searches have been carried out for the particles predicted by supersymmetry theories, and a sampling of these is given. There have also been searches for flavor changing neutral currents in the interactions of the top quark. In addition, searches for excited leptons, leptoquarks and technicolor are summarized.

scholarly journals Search for Light New Physics atBFactories

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Bertrand Echenard
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
New Physics ◽  
Large Datasets ◽  
Higgs Bosons ◽  
The Standard Model ◽  
New Particles

Many extensions of the Standard Model include the possibility of light new particles, such as light Higgs bosons or dark matter candidates. These scenarios can be probed using the large datasets collected byBfactories, complementing measurements performed at the LHC. This paper summarizes recent searches for light new physics conducted by theBABARand Belle experiments.

scholarly journals RECENT STUDIES OF TOP QUARK PROPERTIES AND DECAYS AT HADRON COLLIDERS

2012 ◽  
Vol 27 (33) ◽  
pp. 1230036 ◽  
Author(s):  
V. CHIOCHIA
Keyword(s):  
Elementary Particle ◽  
Standard Model ◽  
Top Quark ◽  
New Physics ◽  
Hadron Colliders ◽  
Statistical Precision ◽  
The Standard Model ◽  
Top Quark Production ◽  
Quark Production ◽  
First Time

The top quark is the heaviest known elementary particle. Observed for the first time in 1995 at the Tevatron by the CDF and D0 experiments, it has become object of several studies aimed to fully characterize its properties and decays. Precise determinations of top quark characteristics verify the internal consistency of the Standard Model (SM) and are sensitive to new physics phenomena. With the advent of the large top quark production rates generated at the LHC, top quark studies have reached unprecedented statistical precision. This review summarizes the recent measurements of top quark properties and studies of its decays performed at the LHC and Tevatron.

scholarly journals Physical implications of electroweak monopole

2019 ◽  
Vol 377 (2161) ◽  
pp. 20190038 ◽  
Author(s):  
Y. M. Cho
Keyword(s):  
Standard Model ◽  
Large Scale ◽  
New Physics ◽  
Dirac Monopole ◽  
Magnetic Current ◽  
Practical Applications ◽  
Large Scale Structures ◽  
The Standard Model ◽  
History Of ◽  
Characteristic Features

The electroweak monopole in the standard model, the existence, characteristic features, cosmological production and physical implications are discussed. The discovery of the Higgs particle has been thought to be the ‘final’ test of the standard model. If the standard model is correct, however, it must have the electroweak monopole as the electroweak generalization of the Dirac monopole. This means that the detection of this monopole should become the final and topological test of the standard model. If detected, it becomes the first magnetically charged and stable topological elementary particle in the history of physics. Moreover, it has deep implications in physics. In cosmology, it could generate the primordial magnetic black holes which could explain the dark matter, become the seed of the large-scale structures of the universe, and be the source of the intergalactic magnetic field. Just as importantly, it could generate the hitherto unknown magnetic current which could have huge practical applications. Furthermore, the existence of the monopole requires us to reformulate the perturbative expansion in quantum field theory. This makes the detection of the electroweak monopole a most urgent issue. We discuss useful tips for the MoEDAL detector at LHC and similar experiments on how to detect the monopole successfully. This article is part of a discussion meeting issue ‘Topological avatars of new physics’.

scholarly journals Type-I 2HDM under the Higgs and electroweak precision measurements

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
Ning Chen ◽  
Tao Han ◽  
Shuailong Li ◽  
Shufang Su ◽  
Wei Su ◽  
...  
Keyword(s):  
Standard Model ◽  
Higgs Doublet ◽  
New Physics ◽  
Higgs Bosons ◽  
Precision Measurements ◽  
Tree Level ◽  
Type I ◽  
Loop Level ◽  
The Standard Model ◽  
Parameter Ranges

Abstract We explore the extent to which future precision measurements of the Standard Model (SM) observables at the proposed Z-factories and Higgs factories may have impacts on new physics beyond the Standard Model, as illustrated by studying the Type-I Two-Higgs-doublet model (Type-I 2HDM). We include the contributions from the heavy Higgs bosons at the tree-level and at the one-loop level in a full model-parameter space. While only small tan β region is strongly constrained at tree level, the large tan β region gets constrained at loop level due to tan β enhanced tri-Higgs couplings. We perform a multiple variable χ2 fit with non-alignment and non-degenerate masses. We find that the allowed parameter ranges could be tightly constrained by the future Higgs precision measurements, especially for small and large values of tan β. Indirect limits on the masses of heavy Higgs bosons can be obtained, which can be complementary to the direct searches of the heavy Higgs bosons at hadron colliders. We also find that the expected accuracies at the Z-pole and at a Higgs factory are quite complementary in constraining mass splittings of heavy Higgs bosons. The typical results are | cos(β − α)| < 0.05, |∆mΦ| < 200 GeV, and tan β ≳ 0.3. The reaches from CEPC, Fcc-ee and ILC are also compared, for both Higgs and Z-pole precision measurements. Comparing to the Type-II 2HDM, the 95% C.L. allowed range of cos(β − α) is larger, especially for large values of tan β.

scholarly journals The CKM unitarity problem: a trace of new physics at the TeV scale?

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
Benedetta Belfatto ◽  
Revaz Beradze ◽  
Zurab Berezhiani
Keyword(s):  
Standard Model ◽  
Decay Constant ◽  
New Physics ◽  
Muon Decay ◽  
Beyond The Standard Model ◽  
Neutron Lifetime ◽  
Gauge Bosons ◽  
Family Symmetry ◽  
Ckm Matrix ◽  
The Standard Model

Abstract After the recent high precision determinations of $$V_{us}$$Vus and $$V_{ud}$$Vud, the first row of the CKM matrix shows more than $$4\sigma $$4σ deviation from unitarity. Two possible scenarios beyond the Standard Model can be investigated in order to fill the gap. If a 4th non-sequential quark $$b'$$b′ (a vector-like weak isosinglet) participates in the mixing, with $$\vert V_{ub'} \vert \sim 0.04$$|Vub′|∼0.04, then its mass should be no more than 6 TeV or so. A different solution can come from the introduction of the gauge horizontal family symmetry $$SU(3)_\ell $$SU(3)ℓ acting between the lepton families and spontaneously broken at the scale of about 6 TeV. Since the gauge bosons of this symmetry contribute to muon decay in interference with Standard Model, the Fermi constant is slightly smaller than the muon decay constant so that unitarity is recovered. Also the neutron lifetime problem, that is about $$4\sigma $$4σ discrepancy between the neutron lifetimes measured in beam and trap experiments, is discussed in the light of the these determinations of the CKM matrix elements.

scholarly journals Measurements of Higgs-boson decays to leptons with the ATLAS detector

2019 ◽  
Author(s):  
Lara Katharina Schildgen
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Precise Measurement ◽  
New Physics ◽  
Muon Decay ◽  
Tau Leptons ◽  
Beyond The Standard Model ◽  
Yukawa Couplings ◽  
Higgs Boson Decaying ◽  
The Standard Model

Since its discovery in 2012, the Higgs boson has served as an important probe for precision measurements of the Standard Model and for searches for new physics beyond the Standard Model. One major goal of the LHC is the precise measurement of the Higgs Yukawa couplings to fermions. The latest ATLAS results of measurements of the Higgs boson decaying to leptons are presented, namely the cross-section measurement of the Higgs boson decay to two tau leptons and the searches for the di-muon decay and lepton-flavour-violating decays of the Higgs boson.

scholarly journals Recent CMS results in top and Higgs physics

2017 ◽  
Vol 32 (29) ◽  
pp. 1730026
Author(s):  
Rebeca Gonzalez Suarez
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Top Quark ◽  
Large Scale ◽  
Top Quarks ◽  
Large Mass ◽  
New Physics ◽  
Higgs Bosons ◽  
Physics Program ◽  
The Standard Model

After the Higgs boson discovery in 2012, the investigation of its properties and compatibility with the Standard Model predictions is central to the physics program of the LHC experiments. Likewise, the study of the top quark is still relevant at the LHC, more than two decades after its discovery at the Tevatron. Top quarks and Higgs bosons are produced at the LHC on a large scale and share a deep connection based on the large mass of the top quark. Both particles provide an excellent laboratory in which to search for new physics: the measurement of their properties tests the foundations of the Standard Model; and they feature prominently in a variety of exotic signals. The coupling of the Higgs boson to the top quark, a fundamental Standard Model parameter, can only be measured directly in processes where the two particles are produced together. The production of a Higgs boson together with one or two top quarks is also sensitive to several exciting new physics effects. A brief overview of the current experimental status of top quark and Higgs boson physics is presented using results from the CMS Collaboration.

scholarly journals Explaining (g − 2)μ with multi-TeV sleptons

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Wolfgang Altmannshofer ◽  
Sri Aditya Gadam ◽  
Stefania Gori ◽  
Nick Hamer
Keyword(s):  
Standard Model ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
New Physics ◽  
Electroweak Symmetry Breaking ◽  
Higgs Bosons ◽  
Electroweak Symmetry ◽  
Flavor Changing ◽  
The Standard Model ◽  
Order Of Magnitude

Abstract We present a supersymmetric extension of the Standard Model in which the new physics contributions to the anomalous magnetic moment of the muon can be more than an order of magnitude larger than in the minimal supersymmetric Standard Model. The extended electroweak symmetry breaking sector of the model can consistently accommodate Higgs bosons and Higgsinos with O(1) couplings to muons. We find that sleptons with masses in the multi-TeV range can comfortably explain the recently confirmed discrepancy in the anomalous magnetic moment of the muon. We discuss additional phenomenological aspects of the model, including its effects on tau flavor changing decays.

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